Throttle device for internal combustion engine

ABSTRACT

An initial opening degree setting mechanism keeps an initial opening degree of a throttle valve larger than that of a fully closed position thereof when no current is supplied to a motor for driving a throttle shaft for the throttle valve. A throttle lever and a sleeve are inserted into the throttle shaft and secured thereto, and a sleeve integrated with a return lever is fitted over the sleeve so as to permit a relative rotational mevement with respect to the sleeve. The sleeve is urged by a return spring in the direction of closing the throttle valve up to the position of the initial opening degree. With the urging force, the return lever is placed to be engageable with the throttle lever. The throttle shaft has a valve opening force applied by a spring for keeping the initial opening degree of the throttle valve near the fully closed position thereof. Thereby parts belonging to the throttle valve initial opening degree setting mechanism are collectively and rationally arranged, a driving load of the throttle actuator motor is reduced and throttle valve control operation is stabilized.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a throttle device for an internalcombustion engine which performs an opening degree control of a throttlevalve for the internal combustion engine with an electrical actuatorand, more specifically, to a throttle device for an internal combustionengine with a mechanism in which an initial opening degree of a throttlevalve for the internal combustion engine, when an engine key switch isturned off, is set larger than that of a fully closed position of thethrottle valve.

2. Description of Conventional Art

In conventional electric throttle control schemes in which a throttlevalve for an internal combustion engine is driven and controlled by anelectrical actuator, it was proposed to set larger an initial openingdegree of the throttle valve (hereinbelow also called as a throttleinitial opening degree), when an engine key switch is turned off, inother words when no current is supplied to a motor for the throttleactuator, than that of fully closed position of the throttle valve whichcorresponds to an opening degree for a normal idling operation aftercompleting a warming-up operation.

One of reasons of setting the initial opening degree as such is toensure a necessary air flow rate for combustion in a prior warming-upoperation during engine starting, in other words in a cold climatestarting. Further, during an idling operation a control is performed inwhich depending on an advancement of the warming-up operation theopening degree of the throttle valve is gradually restricted from theinitial opening degree to that of the fully closed position whichcorresponds to an opening for a normal idling operation.

Other reasons of setting the initial opening degree as such are toensure self pulling for permitting a limp home function in case when athrottle control system malfunctions, to ensure a predetermined air flowrate for preventing a possible engine stop and to prevent the throttlevalve from adhering to the inner wall of a throttle body by such asadhering material and ice pieces contained in the air.

For example, JP(PCT)-A-2-500677 discloses a return spring serving as afirst urging means which urges a throttle valve in its closing directionand a resisting spring serving as a second urging means or a spring usedfor determining an initial opening degree which urges the throttle valvein its opening direction against the return spring wherein the springforce of the resisting spring of the latter at the position of thethrottle initial opening degree is set larger than that of the returnspring and during an engine key switch being turned off a free end ofthe resisting spring is engageably stopped by a stopper at the positionof the throttle valve initial opening degree so as to hold the throttleinitial opening degree.

Further, JP-A-3-271528 discloses the following structure in which asleeve serving as a supporting member as well as one of constitutingelements for a relief lever is fitted in a boss portion on a side wallof a throttle body where an end of a throttle shaft is supported so asto permit free movement in a rotating direction, the relief lever isurged by a return spring serving as a first urging means in thedirection for closing the throttle valve, on one hand, a throttle leveris secured to the throttle shaft and the relief lever is then engaged tothe throttle lever by the spring force of the return spring, and duringno current being supplied to a motor the throttle valve is moved throughthe engagement of the relief lever and the throttle lever and throughthe spring force of the return spring up to a predetermined positionwhere the opening degree of the throttle valve is larger than that atthe fully closed position thereof and is stopped there by a stopper andat this predetermined position the throttle lever is urged in thedirection of opening the throttle valve by making use of a second urgingmeans to thereby hold a throttle initial opening degree.

Still further, JP-A-4-203219 discloses a structure in which a lever issecured at an end of a throttle shaft so as to cross therewith, a returnspring serving as a first urging means applies an urging force to oneend of the lever in the direction of closing the throttle valve, asecond urging means applies an urging force to the other end of thelever in the direction of opening the throttle valve near a throttlefully closed position, and the urging force of the second urging meansis set larger than that of the first urging means when a throttleopening degree is below a predetermined opening degree, in that belowthe throttle initial opening degree to thereby maintain the throttleinitial opening degree.

In these conventional examples, controls of the throttle valve openingdegree are performed through drive controls of their motors based oncontrol signals transmitted from their control systems and when athrottle valve opening degree is desired to be reduced less than thethrottle initial opening degree, a driving torque by the motor iseffected to move the throttle valve in the closing direction against thesecond urging means.

In these sorts of the initial opening degree setting mechanisms such asdisclosed in JP-A-3-271528, since such as the relief lever, the throttlelever being engaged with the relief lever, the first and second urgingmeans and the stopper are disposed at around one end of the throttleshaft, a collective arrangement of these parts is achieved. However, insuch conventional structure, the sleeve constituting one element of therelief lever and serving as a supporting member is fitted into the bossportion formed on the side wall of the throttle body, therefore, whenthe sleeve follows the rotation of the throttle shaft during control ofthe throttle opening degree, then the sleeve slides around the outercircumference of the boss portion to thereby cause a friction betweenthe sleeve and the boss portion which is required to be reduced as muchas possible, because such friction operates as a load with respect tothe return spring and the motor drive.

Further, in connection with the collective arrangement of the parts forthe throttle initial opening degree setting mechanism, when a so calledlimp home mechanism is incorporated which, in case when circuits andactuators for throttle control unit in an electrically controlthrottling system or an electric throttle control system malfunction,permits self pulling by mechanically coupling the acceleration pedalwith the throttle valve, a collective and rational arrangement of theparts of the limp home mechanism is also desired.

In this sort of the limp home mechanism, since the throttle shaft isdriven and controlled by a motor during a steady state traveling, theacceleration lever for the self-pulling never engages with the throttlelever directly connected to the throttle shaft, when the accelerationpedal is depressed. However, during a traction control such as forpreventing slipping the throttle lever is suddenly returned with respectto the acceleration lever and the throttle lever resultantly engageswith the acceleration lever to thereby cause a kick-back of applying areturn force on the acceleration lever which was one of problems to besolved.

Further, both a throttle shaft torque T1 which is provided by the returnspring serving as the first urging means uring the throttle valve in itsclosing direction and another throttle shaft torque T2 which is providedby the spring used for predetermining the initial opening degree andserving as the second urging means urging the throttle valve in itsopening direction are generally designed to satify the following twoinequations in order to keep a predetermined margin at the position ofthe throttle initial opening degree

    T1>Mf×Ge+Vf

    T2>Mf×Ge+Vf

wherein, Mf; friction torque when the motor is standstill, Ge; reductiongear ratio, Vf; necessary torque to be applied on the throttle shaft soas to open the throttle valve.

In JP(PCT)-A-2-500677 and JP-A-4-203219, it is designed that arelationship of T1<T2 stands below a predetermined throttle openingdegree near the throttle fully closed position. On the other hand, inJP-A-3-271528, it is designed to permit a relationship of T1≧T2, becausethe spring force of the return spring serving as the first urging meansis received by the stopper for the initial opening degree and the shafttorque T2 at the position of the throttle initial opening degree can beset without being restricted by the shaft torque T1. Anyway, the firstand the second urging means are designed based on the above twoinequations.

Since T1 is a shaft torque which urges the throttle valve in its closingdirection which is hereinbelow assumed as positive direction and T2 is ashaft torque which urges the throttle valve in its opening directionwhich is hereinbelow assumed as negative direction, as explained above,a shaft torque stepped difference T1-(-T2) between the throttle shafttorques due to the first and second urging means is generated whichsuddenly changes at the reference position of the throttle initialopening degree. Since the larger the shaft torque stepped difference theharder the control of the throttle valve opening degree, it ispreferable to minimize the shaft torque stepped difference in order toincrease an accuracy of the throttle valve control.

SUMMARY OF THE INVENTION

The present invention was achieved in view of the above explainedseveral problems. Thus, an object of the present invention is primarilyto collectively and rationally arrange parts belonging to a throttlevalve initial opening degree setting mechanism and, if required, partsbelonging to other mechanisms including such as a limp home mechanism.Through the enhancement of rationalization with respect to mounting ofthe throttle valve initial opening degree setting mechanism, severaladvantages are achieved such as reduction of frictions inherent to themechanisms, and an improvement in characteristics of the urging means,for example, an improvement in spring characteristics of such as thereturn spring in comparison with conventional devices,, thereby adriving load for a throttle valve actuator is reduced, a throttle valvecontrol operation is stabilized and assembly works of the parts areimproved and simplified.

A throttle device for an internal combustion engine according to firstaspect of the present invention which includes a motor used as anactuator in a throttle control system, a fully closed position settingmechanism for setting a fully closed position of a throttle valve, andan initial opening degree setting mechanism which keeps an initialopening degree of the throttle valve larger than that of the fullyclosed position when no current is supplied to the motor, wherein theinitial opening degree setting mechanism comprises a fitting memberrotatably fitted onto a throttle shaft for the throttle valve, a firsturging means urging the fitting member in the direction of closing thethrottle valve, an engaging means secured to the throttle shaft andbeing engageable with the fitting member via a force due to the firsturging means, a stopper which prevents the fitting member being rotatedbeyond the position of the initial opening degree of the throttle valvein its closing direction, and a second urging means which provides tothe throttle shaft a throttle valve opening force near the fully closedposition so as to keep the initial opening degree of the throttle valve,and wherein in an operating region beyond the initial opening degree ofthe throttle valve the fitting member is normally rotated integrallywith the throttle shaft while being carried on the throttle shaft.

According to the above constitutional structure, under a condition of anengine key switch being turned off, in other words no current beingsupplied to the motor a throttle valve closing force due to the firsturging means is applied to the throttle shaft via the fitting member andthe engaging member securred to the throttle shaft, and the fittingmember is engageably stopped by the stopper at the position of thethrottle initial opening degree, further through the application of thethrottle opening force of the second urging means on the throttle shaftthe throttle valve is kept at the position of the initial opening degreewhich is larger than that of fully closed position.

Further, when the opening degree of the throttle valve is controlled bythe motor in the region beyond the throttle initial opening degree, thefitting member is normally operated integrally with the throttle shaftunder the condition wherein the fitting member is carried on thethrottle shaft, therefore, substantially no friction is generatedbetween the throttle shaft and the fitting member. For this reason, aspring loading force of the first urging means can be limited andresultantly a required throttle shaft torque T1 can be reduced, therebya driving load for the motor is decreased. Further, the shaft torquestepped difference T1-(-T2) between the two throttle shaft torques whichis generated across the reference position of the throttle initialopening degree can also be reduced to thereby enhance the stability ofthe throttle valve drive control.

A throttle device for an internal combustion engine according to asecond aspect of the present invention which includes a motor whichdrives a throttle shaft for performing an open and close control of athrottle valve, a fully closed position setting mechanism for setting afully closed position of a throttle valve, and an initial opening degreesetting mechanism which keeps an initial opening degree of the throttlevalve larger than that of the fully closed position when no current issupplied to the motor, wherein the initial opening degree settingmechanism comprises, as the elements thereof, a throttle lever, a returnlever, a first urging means, a second urging means, a first sleeve and asecond sleeve, and wherein the throttle lever and the first sleeve areinserted into an end of the throttle shaft and are secured there via aclamping force in the axial direction of a nut, the second sleeve beingintegrated with the return lever is fitted to the first sleeve so as topermit a relative rotational movement and further urged by the firsturging means to the position of the initial opening degree in thedirection of closing the throttle valve, through the urging force thereturn lever is caused to be engageable with the throttle lever, and thethrottle shaft is applied of a throttle valve opening force by thesecond urging means so as to keep the initial opening degree of thethrottle valve near the fully closed position.

According to the above constitutional structure, under a condition of anengine key switch being turned off, in other words no current beingsupplied to the motor a throttle valve closing force due to the firsturging means is applied to the throttle shaft via the engagement of thereturn lever and the throttle lever, and the return lever and its secondsleeve are engageably stopped by the stopper at the position of thethrottle initial opening degree, further through the application of thethrottle opening force of the second urging means on the throttle shaftthe throttle valve is kept at the position of the initial opening degreewhich is larger than that of fully closed position.

Further, when the opening degree of the throttle valve is controlled bythe motor in the region beyond the throttle initial opening degree, thesecond sleeve with the return lever is normally operated integrally withthe throttle shaft under the condition wherein the second sleeve withthe return lever is carried on the throttle shaft, more specifically onthe first sleeve, therefore, substantially no friction is generatedbetween the first and second sleeves. For this reason, a spring loadingforce of the first urging means can be limited and resultantly arequired throttle shaft torque T1 can be reduced, thereby a driving loadfor the motor is decreased. Further, the shaft torque stepped differenceT1-(-T2) between the two throttle shaft torques which is generatedacross the reference position of the throttle initial opening degree canalso be reduced to thereby enhance the stability of the throttle valvedrive control. Namely, the above functions and advantages aresubstantially the same as of the first aspect of the present invention.

Still further, according to the second aspect of the present invention,parts belonging to the initial opening degree setting mechanism areinstalled in such a manner that the first sleeve, the second sleeve withthe return lever, the throttle lever and, if required such as spacersare successively inserted into an end of the throttle shaft and areclamped there through a nut, thereby the assembly work of these parts issimplified.

A throttle device for an internal combustion engine according to a thirdaspect of the present invention comprises the above explained returnspring serving as the first urging means and the spring used fordetermining the initial opening degree and serving as the second urgingmeans, wherein a spring holder divided into two parts along the shaftdirection is disposed on the throttle shaft, the spring holder isprovided with two spring receiving spaces one being inside and the otherbeing outside by partitioning the same and with a plurality of cut-outswhich permit the ends of the respective springs received in respectivepartitioned spaces to be led out from the spring holder so as to connectwith predetermined members and one of the return spring and the springused for determining the initial opening degree is received in theoutside space of the spring holder and the other is received in theinside space of the spring holder.

According to the above constitutional structure, when the return springand the spring used for determining the initial opening degree areconstituted by torsion springs such as coil springs, collectivearrangement of parts is achieved as well as an interference between thetwo springs is prevented.

Further, when the return spring is disposed inside space of springholder and the spring used for determining the initial opening degree isdisposed in the outside space of the spring holder, since the springconstant of a spring disposed inside space of the spring holder can bereduced because of the small coil diameter of the spring, the springcharacteristic of the return spring defined by spring loading inordinate and throttle opening degree in abscissa can be flattened asmuch as possible. As a result, a load of the actuator for driving thethrottle valve can be reduced.

A throttle device for an internal combustion engine according to afourth aspect of the present invention which includes a motor used as anactuator in a throttle control system, a fully closed position settingmechanism for setting a fully closed position of a throttle valve, andan initial opening degree setting mechanism which keeps an initialopening degree of the throttle valve larger than that of the fullyclosed position when no current is supplied to the motor, wherein areduction gear mechanism used for amplifying the driving force of themotor is disposed at one end of a throttle shaft for the throttle valvepassing through a throttle body, a screw used for adjusting an openingdegree for an idling operation which is used as a stopper in the fullyclosed position setting mechanism is disposed on a side wall of thethrottle body at the side where the reduction gear mechanism is disposedand another screw used for adjusting the initial opening degree which isused as stopper in the initial opening degree setting mechanism is alsodisposed on a side wall of the throttle body.

According to the above constitutional structure, with the screw used foradjusting the opening degree for an idling operation serving as thestopper in the fully closed position setting mechanism and the screwused for adjusting the initial opening degree serving as the stopper inthe initial opening degree setting mechanism the respective openingdegrees can be freely set, in addition, since the stopper in the fullyclosed position setting mechanism is disposed at the side where thereduction gear mechanism is disposed, the distance between the reductiongear position at which a torque is provided for the throttle shaft andthe stopper which determines the fully closed position is shortened, atorsional force generated on the throttle shaft between the stopper andthe reduction gear is reduced.

Further, when a gear element attached to the throttle shaft in thereduction gear mechanism is formed in a fan shaped gear and the screwused for adjusting the opening degree for an idling operation andserving as the stopper in the fully closed position setting mechanism isdisposed so as to abut to one side of the fan shaped gear, a part of thegear can be served as a stopper engaging member at the side of thethrottle shaft.

A throttle device for an internal combustion engine according to fifthaspect of the present invention comprises:

a motor used as an actuator which drives a throttle shaft for a throttlevalve;

a first stopper for setting a fully closed position of the throttlevalve;

a lever A fitted at an end of the throttle shaft so as to permit arotational movement with respect to the throttle shaft; (whichcorresponds to the fitting member according to the first aspect of thepresent invention and also corresponds to the sleeve with the returnlever according to the second aspect of the present invention);

a return spring which urges the lever A in the direction of closing thethrottle valve;

a lever B which is secured to an end of the throttle shaft and ispermitted to be engageable with the lever A by a spring force due to thereturn spring; (which corresponds to the engaging member according tothe first aspect of the present invention and also corresponds to thethrottle lever according to the second aspect of the present invention);

a second stopper which sets a position where an initial opening degreeof the throttle valve, when no current is supplied to the motor, islarger than the opening degree of the fully closed position of thethrottle valve and prevents the lever A from rotating in the directionof closing from the position of the initial opening degree;

a spring used for determining the initial opening degree which providesa throttle valve opening force to the throttle shaft so as to keep theinitial opening degree;

an acceleration shaft which is disposed in an off-set position withrespect to the throttle shaft and is interlockable with an accelerationpedal; and

a lever C serving as an acceleration lever used for a limp home functionwhich rotates integrally with the accelerating shaft and is engageablewith the lever A when the acceleration pedal rotates beyond apredetermined rotation angle so as to actuate self-pulling function withthe acceleration pedal when the motor is inoperable due tomalfunctioning of an electric throttle control system.

According to the above constitutional structure, like the first aspectof the present invention, the setting of the throttle initial openingdegree and the electrical control of the throttle valve can be achieved,in addition thereto, the following limp home mechanism is actuated whenthe motor becomes inoperative.

When the motor is inoperative and the acceleration pedal is depressedagaint the spring force of the return spring to rotate the accelerationshaft upto a predetermined rotating angle position, the lever C engageswith the lever A fitted to the throttle shaft. Thereby, the lever A isrotated in the direction of opening the throttle valve, and the lever Bsecured to the throttle shaft follows the lever A by the spring force inthe direction of opening due to the spring used for determining thethrottle initial opening degree and opens the throttle valve.

Thus, an emergency self pulling, in other words a limp home function, iseffected. Further, parts of levers used respectively for the throttleinitial opening degree setting mechanism and the limp home mechanism andsprings therefor can be used commonly, therefore, a collective andrational arrangement and use of the parts thereof are achieved.

Further, when the throttle device is normal and is electricallycontrolled and further in case when the tranction control is activated,in particular, when the driver fully depresses the acceleration pedalupon occurrence of a slip and in response thereto the throttle controlsystem effects to rotate the throttle valve in its closing direction soas to prevent the slipping, the lever A may engage with the lever C.However, even if such engagement occurs, the throttle shaft can berotated in its closing direction while leaving the lever A as it is,therefore, the limp home mechanism never operates to disturb theperformance of the traction control.

A throttle device for an internal combustion engine according to a sixthaspect of the present invention which includes a motor used as anactuator in a throttle control system, a fully closed position settingmechanism for setting a fully closed position of a throttle valve, andan initial opening degree setting mechanism which keeps an initialopening degree of the throttle valve larger than that of the fullyclosed position when no current is supplied to the motor, wherein areduction gear mechanism of the motor which drives a throttle shaft forthe throttle valve is disposed at one of the side walls of a throttlebody, a casing portion is formed at the opposit side wall of the oneside wall of the throttle body, an end of the throttle shaft and anacceleration shaft interlocked with an acceleration pedal are introducedinto the casing portion, a throttle position sensor, acceleration pedalposition sensor and the initial opening degree setting mechanism areinstalled within the casing portion and a member supporting theacceleration shaft and acceleration pedal position sensor serves as acover of the casing portion.

According to the above constituting structure, in addition to theinitial opening degree setting mechanism the throttle position sensorand the acceleration pedal position sensor which are used for anelectrical control of the throttle valve can be collectively disposedinside the common casing portion provided at the side wall of thethrottle body. Moreover, since the cover of the casing portion is usedcommonly as the supporting member for the acceleration shaft and theacceleration pedal position sensor, a rationalized use of parts thereofis achieved.

A throttle device for an internal combustion engine according to aseventh aspect of the present invention which includes a motor used asan actuator for driving a throttle valve and a reduction gear mechanism,a throttle sensor for detection position relating to the opening degreeof the throttle valve, and an initial opening degree setting mechanismwhich keeps an initial opening degree of the throttle valve larger thanthat of the fully closed position when no current is supplied to themotor, wherein the reduction gear mechanism and the initial openingdegree setting mechanism are disposed at one side with reference to athrottle body and the throttle position sensor is disposed at the otherside with reference to the throttle body.

A mechanism having a mechanical sliding portion, for example a slidingportion of intermetallic members, such as the reduction gear mechanismis likely to generate weared powders. According to the aboveconstitutional strucure, the reduction gear mechanism and the throttleposition sensor are disposed in a spaced apart relationship via thethrottle body, because of the above spaced arrangement structure aninclusion of the weared powders into the throttle position sensor isprevented and a performance degradation of the throttle position sensoris also prevented.

Further, since the reduction gear mechanism as well as the throttleinitial opening degree setting mechanism are collectively arrangedinside the casing near the motor location, a collective arrangement ofparts thereof is achieved as well as the down sizing the entire throttledevice is also achieved. Moreover, the throttle position sensor can bedesigned to be disposed near the center of the throttle body as much aspossible, resultantly, influences due to deflection and bending of thethrottle shaft is eliminated and a variation of output characteristic ofthe throttle position sensor can be limited.

A throttle device for an internal combustion engine according to eighthaspect of the present invention comprises a first urging means whichurges a throttle valve in its closing direction in a region beyond athrottle valve opening degree defined by a stopper used for setting athrottle initial opening degree and a second urging means which urgesthe throttle valve in its opening direction so as to keep the throttleinitial opening degree near the fully closed position thereof, whereinwhen assuming that a shaft torque in the direction of closing thethrottle valve provided by the first urging means at the position of thestopper used for setting the initial opening degree is T1 and anothershaft torque in the direction of opening the throttle valve provided atthe position of the stopper used for setting the initial opening degreeis T2, the following inequations are satisfied;

    T1≧Mf×Ge+Vf

    T2≦Mf×Ge+Vf

wherein, Mf; friction torque when the motor is standstill, Ge; reductiongear ratio, Vf; necessary torque to be applied on the throttle shaft soas to open the throttle valve.

According to the above constitutional structure, through minimizing thethrottle shaft torque characteristics T1 and T2 the stepped differenceof the throttle shaft torques T1-(-T2) near the position of the throttleinitial opening degree can be reduced, thereby a stabilization of thethrottle drive control is achieved. Further, in case when T2<Mf×Ge+Vf,T2 is slightly sacrificed at the position of the initial opening degreeas illustrated in FIG. 16 which will be explained later and a residenterror is generated at the position of the throttle initial openingdegree. However, in spite of this resident error, if an air flow ratenecessary for a combustion required from the vehicle side during a coldclimate start is ensured, an intended purpose for the initial openingdegree will be satisfied.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross sectional view of a first embodiment according to thepresent invention;

FIG. 2 is a view seen from an arrow A in FIG. 1;

FIG. 3 is an exploded perspective view of the first embodiment accordingto the present invention and FIG. 3A is an isolated exploded view of thelever and return spring shown in FIG. 3;

FIGS. 4A and 4B are cross sectional views of major portions of the firstembodiment according to the present invention;

FIG. 5 is a view for explaining an operating principle of the presentinvention;

FIGS. 6A and 6B are views for explaining a limp home characteristicsincluded in the first embodiment according to the present invention;

FIG. 7 is a view for explaining a throttle shaft torque characteristicbased on the operating principle according to the present invention;

FIG. 8 is a cross sectional view showing a second embodiment accordingto the present invention;

FIG. 9 is an exploded perspective view of a major portion of the secondembodiment according to the present invention;

FIGS. 10A and 10B are cross sectional views of major portions of thesecond embodiment according to the present invention;

FIGS. 11A and 11B are cross sectional views of major portions of a thirdembodiment according to the present invention;

FIG. 12 is an exploded perspective view of a major portion of the thirdembodiment according to the present invention;

FIG. 13 is an exploded perspective view of a major portion of a fourthembodiment according to the present invention;

FIGS. 14A and 14B are cross sectional views of major portions of thefourth embodiment according to the present invention;

FIG. 15 is a cross sectional view of a fifth embodiment according to thepresent invention; and

FIG. 16 is a view for explaining an example of throttle shaft torquecharactristics used in the fifth embodiment according to the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now, several embodiments of the present invention are explained withreference to the drawings.

FIG. 1 is a vertical cross sectional view showing a throttle devicerepresenting a first embodiment according to the present invention, FIG.2 is a view seen from an arrow A in FIG. 1, FIG. 3 is a explodedperspective view thereof and FIGS. 4A and 4B are cross sectional viewsof major portions thereof.

In these drawings a throttle body 15 is, for example, made of analuminium die cast and inside of which an intake air passage or bore 30is formed. In the throttle body 15, a throttle shaft 18 passes throughacross the intake air passage 30 and is supported via bearings 28 and 29so as to permit free rotational movement, and a throttle valve 24 whichcontrols an intake air flow rate through the intake air passage 30 issecured to the throttle shaft 18. Numeral 26 is a pipe which passesengine cooling water to the throttle body 15, thereby the throttle body15 is kept at the temperature of the engine cooling water.

Among side walls of the throttle body 15, at one of right and left sidewalls through which throttle shaft 18 crosses, a bearing receivingportion 15C receiving the bearing 29 and a seal 32 and a casing portion15A receiving a driving use gear group for an electric throttle controlsystem are integrally formed with the throttle body 15, and at theopposite side thereof another bearing receiving portion 15D receivingthe bearing 28 and a seal 31 and a casing portion 15B receiving a limphome mechanism and an initial opening degree setting mechanism for thethrottle valve 24 are disposed.

The limp home mechanism is designed to permit an emergency self pullingof the vehicle with a mechanical acceleration mechanism in case when anelectronic throttling including such as an actuator and a control systemtherefor malfunctions. The initial opening degree setting mechanism isdesigned to set an initial opening degree of the throttle valve 24 whenan engine key switch is turned off, in other words no current issupplied to a motor 12. The initial opening degree of the throttle valve24 is set, for example, at 5°(±0.2°) and also set larger than an openingdegree of throttle valve fully closed position which corresponds to anopening degree ensuring an air flow rate for an idling operation. Theconstitutional structures of the limp home mechanism and the initialopening degree setting mechanism will be explained later. However, thenecessity of setting the initial opening degree is already explained,therefore, the explanation thereof is omitted.

The gear group receiving casing portion 15A is covered by a cover 21which is detachably secured by screws, and gears such as 11, 9A, 9B and10 for a throttle driving system are received in an inner space 20 ofthe casing portion 15A. On the other hand, the casing portion 15Breceives such as acceleration levers 1 and 1', an acceleration shaft 34and an acceleration pedal position sensor 13 and is covered by a cover22 which is detachably secured by screws.

The acceleration lever cover 22 has a boss portion 90 which supports theacceleration shaft 34 passing through the acceleration cover 22 viabearings 93 and 94 and at an end of the acceleration shaft 34 the firstacceleration lever 1 with an acceleration wire connecting portion 33 isfixedly arranged.

Arround the outer circumference of the boss portion 90 a springsupporting member 91 is fitted. The other end of the acceleration shaft34 is introduced into the cover 22 and is fixedly arranged to the secondacceleration lever 1' serving as a cam lever. The fixedly arrangement ofthese levers 1 and 1' is carried out by making use of forcedsandwitching between clamping nuts 35 and 92 disposed at both ends ofthe acceleration shaft 34 and stepped portions formed on theacceleration shaft 34.

Around the outer circumference of the spring supporting member 91 anacceleration use return spring 8 constituted by a coil shaped torsionspring is installed. One end of the return spring 8 is connected to theside of the first acceleration lever 1 and the other end thereof isconnected to the side of the cover 22, thereby the return spring 8 urgesthe acceleration shaft 34,, and the acceleration levers 1 and 1' in thedirection of closing. When an acceleration pedal is depressed, theacceleration levers 1 and 1' are rotated via a wire 44 in the directionof opening against the spring force of the return spring 8.

However, when the throttle shaft 18 is electrically rotated by the motor12, the cam shaped acceleration lever 1 and 1' never transmits a drivingforce to the throttle shaft 18. Numeral 95 is a sealing member.

At one part of the side walls of the throttle body 15, in the drawingsat the bottom part thereof, a motor casing portion 15E is provided in amanner in parallel with the throttle shaft 18 and in the motor casingportion 15E the motor 12 serving as an actuator for the electronicthrottling is received. Such as a DC motor and a stepping motor are usedfor the motor 12.

The inner circumference of the motor casing portion 15E is configuratedin a taper shape so as to facilitate insertion of the motor 12thereinto, and at the deepest end of the motor casing portion 15E anelastic member 27 is placed and at the opening portion of the motorcasing portion 15E a motor securing plate 96 is disposed, thereby, whena screw 97 is clamped, the motor 12 is forcedly sandwiched between theelastic member 27 and the securing plate 96.

A motor gear 11 serving as a pinion gear provided at a shaft 12A of themotor 12 engages with an intermediate gear 9A. The intermediate gear 9Ais designed to have a larger gear ratio than that of the motor gear 11to reduce speed and to increase torque, and this increased rotationaltorque is further transmitted to the throttle shaft 18 via anotherintermediate gear 9B and a throttle gear 10.

The intermediate gears 9A and 9B are an integrated type and are looselyfitted to a gear supporting use shaft 25 which is arranged in parallelwith the throttle shaft 18 so as to permit rotational movement, and oneend of the gear supporting use shaft 25 is press fitted and supported bya bore 98 formed in a side wall of the throttle body 15 and other endthereof is pressed by the cover 21 via a nylon washer 100 to prevent theintermediate gears 9A and 9B from dropping out the gear supporting useshaft 25.

The throttle gear 10 is secured to one end of the throttle shaft 18 byclamping a nut 23 thereto. A fan shaped gear as illustrated in FIG. 3is, for example, used for the throttle gear 10, and when the throttlegear 10 is rotated in the direction of closing the throttle valve 24,the one side of the throttle gear 10 finally hits a screw 7 foradjusting a throttle valve fully closed position, in other words a screwfor adjusting an opening degree for an idling operation or a firststopper which is provided at a side wall of the throttle body 15,thereby further rotation of the throttle shaft 18 in the closingdirection is restricted, thus the fully closed position of the throttlevalve 24 is determined. The throttle valve fully closed position is setat a minimum opening degree which ensures an air flow rate for an idlingoperation after warming-up operation.

Since the throttle device according to the present embodiment employs anelectric throttling system, as far as the driving use motor 12 in thethrottle control system is operating normally, a driving force of themotor 12 provides a rotational torque to the throttle shaft 18 via thereduction gear mechanism.

A driving current is supplied to the motor 12 from a throttle controlmodule (TCM) not shown. The TCM prepares a drive current command signalin the following manner. Namely, using such as an acceleration positionsignal from an acceleration position sensor 13 which detects adepressing amount of an acceleration pedal 53 as shown in FIG. 5 andhereinbelow sometimes called as an acceleration sensor, a throttleopening degree signal from a throttle position sensor 14 which ishereinbelow sometimes called as a throttle sensor, an engine rpm and aslip signal, the command signal is prepared in response to the currentoperating requirement such as a normal engine operating control and atraction control.

In order that a mechanical driving force from the acceleration pedal 53is not transmitted to the throttle shaft 18 as far as the throttlecontrol system is normally operating, the throttle shaft 18 and theacceleration shaft 34 are physically separated and are arranged inoffset and between the throttle shaft 18 and the acceleration shaft 34the acceleration lever 1' and the lever 2 constituting the elements ofthe limp home mechanism are disposed.

Now, the limp home mechanism and the initial opening degree settingmechanism are explained hereinbelow. These two mechanisms in the presentembodiment are disposed at the opposite side where the reduction gearmechanism in the throttle driving system is provided with reference tothe throttle body 15.

The initial opening degree setting mechanism is constituted by a sleeve42 with the lever 2, in other words a lever A, or a return lever whichis fitted to an end of the throttle shaft 18 so as to permit rotarymovement with respect to the throttle shaft 18 and which is hereinbelowcalled as a lever (A) 2, a return spring 4, in other words a firsturging means which urges the sleeve 42 with the lever (A) 2 in thedirection of closing the throttle valve 24, a lever 3, in other words alever B or a throttle lever which is engageable with the lever (A) 2 bya spring force due to the return spring 4 secured to one end of thethrottle shaft 18 and is hereinbelow called as a lever (B) 3, a screw 6for adjusting the initial opening degree, in other words a secondstopper 6 which prevents rotation in the closing direction of the sleeve42 with the lever (A) 2 at the position of the initial opening degreewhen no current is supplied to the motor 12, in other words an enginekey switch is turned off, and a spring 5 used for determining theinitial opening degree, in other words a second urging means whichprovides to the throttle shaft 18 a throttle valve opening force forkeeping the initial opening degree.

A specific installation structure of these elements is explained withreference to FIGS. 3, 3A, 4A and 4B.

As illustrated in FIG. 3, at least one end of the throttle shaft 18 isconfigurated in a flat shape having two parallel faces, from this oneflattened end of the throttle shaft 18 a spacer 50 is inserted upto ashaft stepped portion 18', subsequently a washer 51 is insertedthereinto, thereafter, a chip 38 with the spring 5 used for determiningthe initial opening degree is inserted thereinto under engagementcondition, then after a nylon washer 43 the sleeve 42 with the lever (A)2 is fitted with a play into the throttle shaft 18 via a sleeve 45,further, the lever (B) 3 is inserted into the throttle shaft 18 underengagement condition and finally a nut 47 is clamped to the throttleshaft via a washer 46.

As illustrated in FIG. 4 (A), one end of the first sleeve 45 abuts tothe chip 38 due to the clamping by the nut 47 and the other end thereofabuts to the lever (B) 3,, thereby the first sleeve 45 is secured aroundthe circumference of the throttle shaft 18. The clamping force by thenut 47 is only provided for the lever (B) 3, the first sleeve 45 and thechip 38, and not for the second sleeve 42 with the lever (A) 2 which isfitted around the circumference of the first sleeve 45 to thereby permitrelative rotational movement of the second sleeve 42 with respect to thethrottle shaft 18 and the first sleeve 45.

As illustrated in FIG. 4B, over the inner face of the second sleeve 42solid lubricating member 52, in other words a dry bearing such asfluororesin coating is applied.

The lever (A) 2 includes arm portions 2A, 2B, 2C and 2D, and is insertedthrough a center attachment bore 2E into the outer circumference of thesecond sleeve 42 serving as a fitting member and is integrated with themetal sleeve 42 by cauking.

The arm portions 2A of the lever (A) 2 is set to be engageable with thelever (B) 3, a projection or a roll pin 2B' forming a part of the armportion 2B is set to be engageable with the acceleration lever or camlever 1', a projection 2C' forming a part of the arm portion 2C is fixedto one end 5A of the spring 5 used for determining the initial openingdegree and the arm portion 2D is set to be engageable to the screw orstopper 6 for adjusting the initial opening degree provided at a sidewall of the throttle body 15. The other end 5B of the spring 5 used fordetermining the initial opening degree is connected to the chip 38.

In the present embodiment, both the return spring 4 and the spring 5used for determining the initial opening degree respectively use aspiral spring.

One end 4B of the return spring 4 is fixed to the second sleeve 42 andthe other end 4A is fixed to the pin 37 provided at a side wall of thethrottle body, and through action of the spring force of the returnspring 4 the arm portion 2A of the lever (A) 2 engages with the lever(B) 3. With this engagement the return spring 4 urges the throttle shaft18 and resultantly the throttle valve 24 in its closing direction.

An exemplary operation of the present embodiment is explained withreference to FIG. 5, a diagram illustrating a principle of the presentinvention and FIGS. 6A, 6B and 7.

When the engine key switch is turned off, in that no current is suppliedto the motor 12, through action of the spring force due to the returnspring 4 the lever (A) 2 urges via the lever (B) 3 the throttle shaft 18in the closing direction and the throttle valve 24 is returned to theposition corresponding to the initial opening degree. At the position ofthe initial opening degree, the arm portion 2D of the lever (A) 2 abutsto the stopper 6, thereby, further rotation of the lever (A) 2 in theclosing direction is prevented.

With the provision of the stopper 6, the spring force due to the returnspring 4 is ineffected from the initial opening degree θ2 of thethrottle valve 24 to the fully closed position thereof, and near thefully closed position of the throttle valve 24, in that between thefully closed position and the initial opening degree θ2 of the throttlevalve 24, the already explained spring 5 used for determining theinitial opening degree is effected, in that a throttle valve openingforce is applied onto the throttle shaft 18, thereby the initial openingdegree of the throttle valve 24 is kept.

An urging force P1 in the closing direction due to the return spring 4and an urging face P2 in the opening direction due to the spring 5 usedfor determining the initial opening degree are respectively determinedto keep a relationship of P1≧P2, in other words a shaft torque T1 in theclosing direction due to the urging force P1 and a shaft torque T2 inthe opening direction due to urging force P2 are determined to keep arelationship of T1>T2.

When such initial opening degree is kept, even if the throttle valve 24is ice-bonded during a prior warming up operation in a cold climate, anecessary air flow rate for the engine starting can be ensured.

When controlling the throttle valve 24 to the fully closed position, inthat when performing an idling operation after warming up operation, thethrottle shaft 18 is rotated in the closing direction against the springforce due to the spring 5 used for determining the initial openingdegree with the driving force by the motor 12 based on an idling controlcommand value. In this instance, in a range between the initial openingdegree and the fully closed position the lever (B) 3 disengages from thelever (A) 2 as illustrated by a broken line 3' in FIG. 5 and performs avalve closing operation integrally with the throttle shaft 18.

When controlling an opening degree or open and close of the throttlevalve 24 in a range exceeding the initial opening degree θ2 under anormal operating condition, the driving force of the motor 12 istransmitted to the throttle shaft 18 via the reduction gear mechanism9A, 9B, 10 and 11, and the opning degree of the throttle valve 24 iscontrolled depending on balancing between the driving force and thespring force due to the return spring 4. At this instance, the lever (A)2 engages with the lever (B) 3 and the second sleeve 42 with the lever(A) 2 is carried on the throttle shaft 18 via the first sleeve 45 and isrotated integrally with the throttle shaft 18.

When the vehicle is under a traction control, for example when thedriver fully depresses the acceleration pedal 53 in response to a slipoccurrence to cause a large rotational displacement of the accelerationlever 1' and on the other hand, through a command from the TCM the motor12 controls the throttle valve 24 in its closing direct so as to preventa slipping, the lever (A) 2 engages in its return course with theacceleration lever 1' and is prevented further rotation in the closingdirection. Even when this condition is caused, the lever (B) 3disengages from the lever (A) 2 and is rotated in the closing directionagainst the spring force due to the spring 5 used for determining theinitial opening degree integrally with the throttle shaft 18, thereby,the control in the direction closing the throttle valve 24, in otherwords a traction control can be performed without troubles.

When the above condition occurs that the lever (A) 2 engages with theacceleration lever 1' when performing a traction control, a phenomenonin that a kick back phenomenon is caused that the spring force due tothe return spring 4 is applied on the acceleration lever 1' via thelever (A) 2 as an impact.

This kick back phenomenon occurs, when the acceleration pedal 53 isdepressed and the acceleration shaft 34 rotates more than θ1 asillustrated in FIG. 6A, wherein θ1 is an angle when through rotation ofthe acceleration shaft 34 by depression of the acceleration pedal 53 theacceleration lever 1' is placed in an engageable condition with thelever (A) 2 at the side of the throttle shaft 18 during a limp homeoperation, however, when an inclination of a cam characteristic definedby the throttle valve opening degree as ordinate and acceleration pedalopening degree, in that rotating angle of accelerations shaft asabscissa is reduced as much as possible, the acceleration lever 1'receives the spring force of the retun spring 4 at a position where thespring loading thereof is small in case when a traction control iseffected where the kick back phenomenon is in particular likely tooccur, therefore, the amount of the kick back is reduced.

However, since it is necessary to ensure a throttle opening degree θ3which is required to carry out a self pulling during a limp homeoperation, a middle portion of the cam characteristic defined bythrottle opening degree and acceleration opening degree is provided anon-linear characterisation as illustrated by a broken line in FIG. 6Amoving below a stright line inclination by making use of a cam shape ofthe acceleration lever 1'.

In the present embodiment, the respective angles θ1, θ2 and θ3 are setas follows as shown in FIG. 6B, in that θ1=30°, the initial openingdegree θ2=5° and a throttle opening degree necessary for a limp homeoperation θ3=7°.

The second sleeve 42 performs a relative rotation on the first sleeve 45in a range between the initial opening degree θ2 and the fully closedposition of the throttle valve 24, further as explained above evenduring the traction control the second sleeve 42 may perform a relativerotation on the first sleeve 45. The friction caused by the slidingmovement is reduced by the solid lubricating member 52.

The limp home mechanism operates in the following manner.

When such as the throttle control system and the motor 12 fail, thethrottle valve 24 is returned to the position of the initial openingdegree by the spring force due to the return spring 4. Under thiscondition, when the acceleration pedal 53 is depressed, through arelative rotation of the acceleration shaft 34 with respect to thethrottle shaft 18 a cam lever 1'A of the acceleration lever 1 engageswith the lever (A) 2, and the lever (A) 2 is rotated in the direction ofopening the throttle valve 24 as illustrated by a dot and chain line inFIG. 5. The throttle shaft 18 and the lever (B) 3 follow the rotation inthe opening direction of the lever (A) 2 by the spring force due to thespring 5 used for determining the initial opening degree and opens thethrottle valve 24 to permit a self pulling by the acceleration pedal 53,in that a limp home operation.

In this instance, in order to ensure the limp home operation, it isnecessary to satisfy the following inequations with regard to the shafttorque T1 determined by the urging force P1 due to the return spring 4at least in a range between the initial opening degree θ2 and thethrottle valve fully closed position, and the shaft torque T2 determinedby the urging force P2 due to the spring 5 used for determining theinitial opening degree at least in a range between the throttle valvefully closed position and the limp home operating region;

    T1>Mf×Ge+Vf

    T2>Mf×Ge+Vf

wherein, Mf; friction torque when the motor is standstill, Ge; reductiongear ratio, Vf; necessry torque to be applied on the throttle shaft soas to open the throttle valve.

According to the present embodiment the following advantages areobtained.

a) The second sleeve 42 with the lever (A) 2 used for driving thethrottle shaft 18 is carried on the throttle shaft 18 and is rotatedintegrally with the first sleeve 45 in a substantial opening degreerange between the initial opening degree and the throttle valve fullyclosed position except that under a condition when the accelerationpedal 53 is fully depressed during a traction control the motor 12effects to close the throttle valve 24, therefore, a possible frictionbetween the second sleeve 42 and the first sleeve 45 is almosteliminated.

Accordingly, the spring force P1 due to the return spring 4 is reduced,resultantly the required shaft torque T1 for the throttle shaft 18 isreduced as well as the driving load for the motor 12 is also reduced.Further, the shaft stepping torque T1-(-T2) between the throttle shafttorques which is caused across the reference position of the throttleinitial opening degree is reduced, thereby a stability of the throttledrive control is enhanced.

b) Constitutional elements of the initial opening degree settingmechanism such as the spacer 50, the washer 51, the chip 38 with thespring 5 used for determining the initial opening degree, the firstsleeve 45, the return spring 4, the second sleeve 42 with the lever (A)2 and the lever (B) 3 can be assembled by simply inserting successivelyinto the throttle shaft 18 and clamping by a nut, thereby aninstallation work thereof is rationalized.

c) The initial opening degree setting mechanism, the limp homemechanism, the throttle sensor 14 and the cover 22 for the casingportion 15B are collectively arranged, moreover, a part of the mechanismparts is used in common, the number and structure of the parts arerationalized and a down sizing of the throttle device is realized.Further, spiral springs are used respectively for the return spring 4and the spring 5 used for determining the initial opening degree afurther compact throttle device is realized.

Further, when such spiral springs are used, ones having a small springconstant can be easily designed, resultantly a reduction of driving loadfor the motor 12 is enhanced.

d) Both the stopper 7 for the fully closed position setting mechanism orthe screw used for adjusting an opening degree for an idling operationand the stopper 6 for the initial opening degree setting mechanism orthe screw used for adjusting the initial opening degree can freely setthe required opening degrees, further both stoppers are providedrespectively on the opposing side walls of the throttle body, the bothstoppers can be easily identified without puzzling in view of such asthe directions of the side walls and the existance of the reduction gearmechanism and the initial opening degree setting mechanism, thereby anerroneous identification of both stoppers is eliminated and resultantlyan erroneous adjustment is prevented.

Further, the stopper 7 for the fully closed position setting mechanismor the screw used for adjusting an opening degree of an idling operationis disposed to abut to one side of the fan shaped gear 10 in thereduction gear mechanism, a part of the gear can be served as a stopperengaging member at the side of the throttle shaft 18.

e) Even when the limp home mechanism and the initial opening degreesetting mechanism are mixedly arranged, the operation of the throttleshaft 18 during a traction control is smoothly performed without beingdisturbed by the limp home mechanism.

Further, with the provision of the non-linear characteristic asillustrated by the broken line in FIG. 6A for the moving characteristicof the acceleration lever 1' in the limp home mechanism, a possibleoccurrence of kick back during a traction control is effectivelysuppressed.

Now, a second embodiment according to the present invention is explainedwith reference to FIGS. 8 through 10, wherein FIG. 8 is a vertical crosssectional view of the second embodiment, FIG. 9 is an explodedperspective view of a major portion thereof and FIGS. 10A and 10B arecross sectional views of major portions thereof.

The structural principle of the present embodiment is substantially thesame as that of the first embodiment except that a part of the partsused therein is modified, therefore, only the modification is explainedhereinbelow. Further, elements in the drawings bearing identicalnumerical references as in the first embodiment show the same orequivalent elements as those of the first embodiment which also appliedto all the elements in other embodiments explained later.

In the present embodiment, a coil shaped torsion spring 63 and a coilshaped torsion spring 64 are respectively used for the return spring andthe spring used for determining the initial opening degree.

Other than the lever (B) 3, lever (B') 3' is fixedly arranged at one endof the throttle shaft 18, between these fixed levers 3 and 3' the sleeve45 is arranged which is secured on the throttle shaft 18 by clamping thenut 47 and arround the outer circumference of the sleeve 45 the sleeve42 with the lever (A) 2 is fitted so as to permit rotation with respectto the sleeve 45.

Around the outer circumference of the sleeve 42 over the throttle shaft18, spring holders 61 and 62 each having a flange are arranged with aspace in the axial direction so as to permit free movement in therotational direction.

The spring holders 61 and 62 respectively include inner cylindricalportions 61A and 62A which fit around the outer circumference of thesleeve 42 and outer cylindrical portions 61B and 62B which partitionsspring setting space into two spaces, in that inside space and outsidespace as illustrateted in FIG. 10A, and in the present embodiment, thereturn spring 63 is arranged in the inside setting space and the spring64 used for determining the initial opening degree is arranged in theoutside setting space.

Further, in the spring holders 61 and 62, cut-outs or spring end leadingout portions 67 and 68 as illustrated in FIG. 9 are formed which areused to lead out end portions 63A and 64B of the return spring 63arranged in the inside setting space to the outside. The end portion 63Aof the return spring 63 is fixed through the cut-out 68 to the pin 37provided at the side wall of the throttle body 15 and the other endportion 63B is fixed through the cut-out 67 to the arm portion 2D of thelever (A) 2.

One end 64A of the spring 64 used for determining the initial openingdegree which is disposed in the outer space of the spring holders 61 and62 is fixed to the lever (B') 3' secured to the throttle shaft 18, andthe other end 64B thereof is fixed to the arm portion 2D of the lever(A) 2.

In the present embodiment, the arm portion 2A of the lever (A) 2 isengaged with the lever (B) 3 secured to the throttle shaft 18 by thereturn spring 63 and the throttle shaft 18 is urged in the direction ofclosing the throttle valve 24. The lever (A) 2 is prevented to rotatefurther in the closing direction when abutting to the screw 6 foradjusting the initial opening degree like the first embodiment.

The spring 64 used for determining the initial opening degree urges thethrottle shaft 18 in the opening direction thereof via the lever (B') 3'so as to keep the initial opening degree near the fully closed positionthereof.

Further, the divided spring holders 61 and 62 receive the spring forceof the springs 63 and 64 in their axial direction and are pressed to thelevers 3 and 3'.

According to the present embodiment, the following advantages inaddition to those obtained in the first embodiment are further obtained.

f) Since the spring holder is constituted by two pieces of springholders 61 and 62 arranged in the axial direction with a space and eachof the spring holder pieces is respectively provided with the inner andouter cylindrical partition walls 61A, 62A and 61B, 62B, an inside andoutside double arrangement structure therefor is realized which preventsinterference between the return spring 63 and the spring 64 used fordetermining the initial opening degree, thereby, the springs are easilyinstalled into the spring holder while achieving a collectivearrangement of the parts thereof.

g) Further, because the return spring 63 is placed inside of the springholder and the spring 64 used for determining the initial opening degreeis placed outside thereof, the coil diameter accordingly the springconstant of the return spring 63 placed inside thereof can be selectedsmaller than those of the spring 64, thereby, the spring characteristicof the return spring 63 defined by spring loading as ordinate andthrottle valve opening degree as abscissa can be flattened as much aspossible, and resultantly, the load of the actuator for driving thethrottle valve 24 is lightened.

However, alternatively, the return spring 63 can be placed outside spacein the spring holder and the spring 64 used for determining the initialopening degree can be placed inside space thereof.

Now, a third embodiment is explained with reference to FIGS. 11A, 11Band 12.

FIGS. 11A and 11B are cross sectional views of major portions of thethird embodiment according to the present invention, and FIG. 12 is anexploded perspective view thereof. Although not illustrated in FIGS.11A, 11B and 12, the arrangement and installation structure of theintake air passage 30 in the throttle body 15, the throttle valve 24,the reduction gear mechanism 9A, 9B, 10 and 11, the acceleration shaft34 supported on the acceleration cover 22 and the levers 1 and 1' aresubstantially the same as those in the first and second embodiments.

In the present embodiment, one of the return spring 63 and the spring 5used for determining the initial opening degree is a coil shaped torsionspring and the other is a sprial shaped torsion spring. Specifically, acoil shaped torsion spring is used for the return spring 63 and a spiralshaped torsion spring is used for the spring 5 used for determining theinitial opening degree.

Further, in place of the sleeve 42 in the preceeding embodiments, asleeve 70 with the lever (A) 2 is used.

The sleeve 70 is constituted by, in addition to the lever (A) 2, aninner cylindrical portion 70A which is fitted on the sleeve 45 so as topermit rotational movement thereto and an outer cylindrical portion 70Bprovided outside of the inner cylindrical portion 70A as illustrated inFIGS. 11A and 11B.

The length of the inner cylindrical portion 70A is cut shorter than thatof the outer cylindrical portion 70B, and in the inner space formed inthe sleeve 70 by cutting the inner cylindrical portion 70A the spring 5used for determining opening degree is set on the throttle shaft 18 viathe chip 38, the one end 5A of the spring 5 is fixed to a cut-out 70Cprovided at the sleeve 70 as illustrated in FIG. 12 and the other end 5Bthereof is fixed to the chip 38.

In the outer cylindrical portion 70B of the sleeve 70, spring holders 71and 72 arranged in axial direction with a space are fittedly installed.

The return spring 63 is supported by the spring holders 71 and 72, andone end 63A of the return spring 63 is fixed to the pin 37 on thethrottle body 15 via a cut-out 72A provided at the spring holder 72 andthe other end 63B thereof is fixed to the arm portion 2D of the lever(A) 2.

According to the present embodiment, in addition to the advantagesobtained by the first embodiment the following advantage is obtained.

h) Even when different types of springs such as a coil shaped torsionspring and a spiral shaped torsion spring are used respectively for thereturn spring and the spring used for determining the initial openingdegree, these two types of springs are collectively arranged in a singlesleeve, thereby a compact throttle device is realized.

Now, a fourth embodiment according to the present invention is explainedwith reference to FIGS. 13, 14A and 14B, wherein FIG. 13 is an explodedperspective view of the fourth embodiment and FIGS. 14A and 14B arecross sectional views of major portions thereof.

In the present embodiment, one of the return spring and the spring usedfor determining the initial opening degree is a spiral shaped torsionspring and the other is a tension spring. In order to achieve a compactarrangement of the throttle device in the present embodiment the initialopening degree setting mechanism is arranged in the side of thereduction gear mechanism for the throttle valve driving system. In thedrawings only the throttle gear 10 in the reduction gear mechanism isillustrated and the illustration of the gears 9A, 9B and 11 is omitted.

As illustrated in FIG. 13, in the present embodiment, from one end ofthe throttle shaft 18 at the side of the reduction gear mechanism thethrottle gear 10, the lever (B) 3, the return spring 4, the sleeve 42with the lever (A) 2, washer 51' and the sleeve 45 are successivelyinserted and clamped by the nut 23. A spiral spring is used for thereturn spring 4, and a tension spring 85 is used for the spring used fordetermining the initial opening degree which will be explained below.

In the same manner as in the preceeding embodiments, the sleeve 45 issecured on the throttle shaft 18 through a mutual action between theclamping by the nut 23 and the throttle shaft step 18' and around theouter circumference of the sleeve 45 the sleeve 42 is fitted so as topermit rotational movement thereof with respect to the sleeve 45 and thethrottle shaft 18.

One end 4A of the return spring 4 is fixed to the pin 37 provided at thethrottle body 15 as illustrated in FIG. 14A and the other end thereof isfixed to the sleeve 42, thereby, the return spring 4 urges the sleeve 42and the lever (A) 2 in the direction of closing the throttle valve 24.

On the other hand, the arm portion 3A of the lever (B) 3 is disposed tobe engageable with the arm portion 2A of the lever (A) 2, and the armportion 3B thereof is fixed to one end 85B of the spring 85 used fordetermining the initial opening degree and the other end 85A of thespring 85 is fixed to the arm 2C of the lever (A) 2.

In the present embodiment like the preceeding embodiments, when theengine key switch is turned off, the initial opening degree settingmechanism operates to transmit the spring force of the return spring 4via the engagement of the lever (A) 2 and the lever (B) 3 to thethrottle shaft 18 to abut to the arm portion 2D of lever (A) 2 at theposition of the initial opening degree, and with the spring force of thespring 85 used for determining the initial opening degree at this momentthe initial opening degree of the throttle valve 24 is kept.

When the motor 12 serving as a throttle actuator is driven from thisposition in the closing direction against the tension force of thespring 85 used for determining the initial opening degree, and the fullyclose control of the throttle valve 24 is effected at the position ofthe adjusting screw 7.

The throttle sensor 14 is also arranged on a side wall face of thethrottle body 15 at the side of the reduction gear mechanism.

In the present embodiment substantially the same advantages obtained inthe preceeding embodiments are also obtained, in addition the followingadvantage is obtained.

i) The reduction gear mechanism for the throttle driving system and theinitial opening degree setting mechanism can be collectively arranged.Further, the reduction gear mechanism and the return spring and thespring used for determining the initial opening degree are arrangedclosely along the throttle shaft 18, thereby mutually interferingtorques in opposing directions can be reduced.

FIG. 15 is a cross sectional view illustrating a fifth embodimentaccording to the present invention. The present embodiment relates to atype of throttle device with no limp home mechanism, in that a fullyelectric type of throttle device, wherein the acceleration shaft, theacceleration lever and the acceleration sensor are separately disposedoutside the throttle body, because the acceleration mechanism is usedfor generating signals relating to an acceleration pedal position and isnot directly related to the open and close operation of the throttlevalve.

In the present embodiment, the initial opening degree setting mechanismis also arranged at the side of the reduction gear mechanism for thethrottle driving system located at one end of the throttle shaft 18. Thereturn spring 4 and the spring 5 used for determining the initialopening degree are installed in substantially the same manner as in thefirst embodiment. At one end of the throttle shaft 18, the throttle gear11, the lever (B) 3 and the chip 38 with the spring 5 used fordetermining the initial opening degree are successively arrangedinmovably and the return spring 4 and the sleeve 42 with the lever (A) 2are fitted via the sleeve 45, then the assembly is clamped by the nut 47so as to permit rotational movement of the sleeve 42 over the sleeve 45.

One end 4A of the return spring 4 is fixed to the pin 37 on the throttlebody 15 and the other end thereof is fixed to the sleeve 42.

The arm portion 3A of the lever (B) 3 is disposed to be engageable withthe lever (A) 2 beyond the spring 5 used for determining the initialopening degree and the return spring 4.

One end 5A of the spring 5 used for determining the initial openingdegree is fixed to the arm portion 3A of the lever (B) 3 and the otherend thereof is fixed to the chip 38. In the present embodiment, theillustration of the screw 6 for adjusting the initial opening degree andthe screw 7 for adjusting the fully closed position is omitted, however,these screws are arranged in the casing portion 15A formed integrallywith the throttle body 15. The principle of the initial opening degreesetting operation according to the present embodiment is substantiallythe same as in the preceeding embodiments, the explanation thereof isomitted.

In the present embodiment advantages except for those relating to thelimp home function obtained in the preceeding embodiments are likelyobtained, in addition the following advantage is obtained.

j) In the present embodiment, the throttle shaft torque characteristicsT1 and T2, in other words P1 and P2 characteristics at the position ofthe stopper used for setting the initial opening degree are set in thefollowing inequations.

    T1≧Mf×Ge+Vf

    T2≦Mf×Ge+Vf

wherein, Mf; friction torque when the motor is standstill, Ge; reductiongear ratio, Vf; necessary torque to be applied on the throttle shaft soas to open the throttle valve.

When setting the throttle shaft torque characteristics T1 and T2according to the above inequations, the throttle shaft torquecharacteristics are minimized and the throttle shaft torque stepT1-(-T2) near the position of the throttle initial opening degree can bereduced, thereby, the throttle drive control can be stabilized. Further,in case when T2<Mf×Ge+Vf, T2 is slightly sacrificed at the position ofthe initial opening degree as illustrated in FIG. 16 and a residenterror is generated at the position of the throttle initial openingdegree. However, in spite of this resident error, if an air flow ratenecessary for a combustion required from the vehicle side during a coldcliminate start is ensured, an intended perpose for the initial openingdegree is satisfied.

k) Further, in the present embodiment, the reduction gear mechanism andthe initial opening degree setting mechanism are arranged at one sidewith reference to the throttle body 15, and the throttle position sensoris arranged at the other side.

A mechanism having a mechanical sliding portion, for example a slidingportion of intermetallic members, such as the reduction gear mechanismis likely to generate weared powders. According to the aboveconstitutional structure, the reduction gear mechanism and the throttleposition sensor are disposed in a spaced apart relationship via thethrottle body, because of the above spaced arrangement structure aninclusion of the weared powders into the throttle position sensor isprevented and a performance degradation of the throttle position sensoris also prevented.

Further, since the reduction gear mechanism as well as the throttleinitial opening degree setting mechanism are collectively arrangedinside the casing near the motor location, a collective arrangedment ofthe parts thereof is achieved as well as the down sizing of the entirethrottle device is also achieved. Moreover, the throttle position sensorcan be designed to be disposed near the center of the throttle body asmuch as possible, resultantly, influences due to deflection and bendingof the throttle shaft is eliminated and a variation of outputcharacteristic of the throttle position sensor can be limited.

According to the present invention, parts belonging to a throttle valveinitial opening degree setting mechanism and, if required, partsbeloging to other mechanisms including such as a limp home mechanism arecollectively and rationally arranged, while improving mountingcharacteristics of these mechanisms, and further, a reduction offrictions inherent to the mechanisms, and an improvement incharacteristic of urging means, for example an improvement in springcharacteristics of such as the return spring in comparison withconventional devices are achieved, thereby a driving load for a throttlevalve actuator is reduced, and a throttle valve control operation isstabilized.

We claim:
 1. A throttle device for an internal combustion engineincluding a motor used as an actuator in a throttle control system, afully closed position setting mechanism for setting a fully closedposition of a throttle valve, and an initial opening degree settingmechanism which keeps an initial opening degree of the throttle valvelarger than that of the fully closed position when no current issupplied to the motor, wherein said initial opening degree settingmechanism comprising a fitting member rotatably fitted onto a throttleshaft for the throttle valve, a first urging device urging the fittingmember in the direction of closing the throttle valve, an engagingdevice secured to the throttle shaft and being engageable with thefitting member via a force due to the first urging device, a stopperwhich prevents the fitting member being rotated beyond the position ofthe initial opening degree of the throttle valve in a closing directionthereof, and a second urging device which provides to the throttle shafta throttle valve opening force near the fully closed position so as tokeep the initial opening degree of the throttle valve, and, in anoperating region beyond the initial opening degree of the throttlevalve, the fitting member is normally rotated integrally with thethrottle shaft while being carried on the throttle shaft.
 2. A throttledevice for an internal combustion engine according to claim 1, whereinsaid fitting member is a movable sleeve having a lever engageable withsaid engaging device secured at the side of said throttle shaft, andsaid movable sleeve is fitted to a stationary sleeve secured to saidthrottle shaft so as to permit a rotational movement with respect tosaid stationary sleeve.
 3. A throttle device for an internal combustionengine including a motor which drives a throttle shaft for performing anopen and close control of a throttle valve, a fully closed positionsetting mechanism for setting a fully closed position of the throttlevalve, and an initial opening degree setting mechanism which keeps aninitial opening degree of the throttle valve larger than that of thefully closed position when no current is supplied to the motor, whereinsaid initial opening degree setting mechanism comprising, as theelements thereof, a throttle lever, a return lever, a first urgingdevice, a second urging device, a first sleeve and a second sleeve, andthe throttle lever and the first sleeve are arranged in an end of thethrottle shaft and secured thereat via a clamping force in an axialdirection of a nut, the second sleeve being integrated with the returnlever is fitted to the first sleeve so as to permit a relativerotational movement and further urged by the first urging device to theposition of the initial opening degree in the direction of closing thethrottle valve, through the urging force the return lever is caused tobe engageable with the throttle lever, and the throttle shaft has athrottle valve opening force applied thereto by the second urging deviceso as to keep the initial opening degree of the throttle valve near thefully closed position.
 4. A throttle device for an internal combustionengine according to claim 1, wherein at least one of the first andsecond urging devices is a spiral spring.
 5. A throttle device for aninternal combustion engine according to claim 2, wherein at least one ofthe first and second urging devices is a spiral spring.
 6. A throttledevice for an internal combustion engine according to claim 3, whereinat least one of the first and second urging devices is a spiral spring.7. A throttle device for an internal combustion engine which includes amotor used as an actuator for driving a throttle valve, a return springwhich urges the throttle valve in the direction of closing the same and,when the motor is turned off, causes to return the throttle valve to aposition of an initial opening degree thereof which is larger than thatof a fully closed position thereof, and a spring used for determiningthe initial opening degree which, when the motor is turned off, urgesthe throttle valve in the direction of opening the same near the fullyclosed position thereof so as to keep the initial opening degreethereof, wherein, on a throttle shaft for the throttle valve, a springholder divided into two parts in the axial direction of the throttleshaft is disposed and provided with two spring receiving spaces onebeing inside and the other being outside by partitioning the same andwith a plurality of cut-outs which permit the ends of the respectivesprings received in respective partitioned spaces to be led out from thespring holder so as to connect with predetermined members, whereby oneof the return spring and the spring used for determining the initialopening degree is received in the outside space of the spring holder andthe other is received in the inside space of the spring holder.
 8. Athrottle device for an internal combustion engine according to claim 7,wherein the return spring is disposed in the inside space of the springholder and the spring used for determining the initial opening degree isdisposed in the outside space of the spring holder.
 9. A throttle devicefor an internal combustion engine according to claim 7, wherein a firstlever is fitted to the throttle shaft so as to be permitted a rotationalmovement with respect thereto, second and third levers are secured tothe throttle shaft, one end of the return spring which is received inthe spring holder is fixed to a throttle body of the throttle valve andthe other end thereof is fixed to the first lever, the first lever andthe second lever are arranged to be engageable each other by a springforce due to the return spring, and one end of the spring used fordetermining the initial opening degree is fixed to the first lever andthe other end thereof is fixed to the third lever.
 10. A throttle devicefor an internal combustion engine according to claim 8, wherein a firstlever is fitted to the throttle shaft for rotational movement withrespect thereto, second and third levers are secured to the throttleshaft, one end of the return spring which is received in the springholder is fixed to a throttle body of the throttle valve and the otherend thereof is fixed to the first lever, the first lever and the secondlever are arranged to be engageable each other by a spring force due tothe return spring, and one end of the spring used for determining theinitial opening degree is fixed to the first lever and the other endthereof is fixed to the third lever.
 11. A throttle device for aninternal combustion engine which includes a motor used as an actuator ina throttle control system, a fully closed position setting mechanism forsetting a fully closed position of a throttle valve, and an initialopening degree setting mechanism which keeps an initial opening degreeof the throttle valve larger than that of the fully closed position whenno current is supplied to the motor, wherein a reduction gear mechanismused for amplifying the driving force of the motor is disposed at oneend of a throttle shaft for the throttle valve passing through athrottle body, a screw used for adjusting an opening degree for anidling operation which is used as a stopper in the fully closed positionsetting mechanism is disposed on a side wall of the throttle body at theside where the reduction gear mechanism is disposed and another screwused for adjusting the initial opening degree which is used as a stopperin the initial opening degree setting mechanism is also disposed on aside wall of the throttle body.
 12. A throttle device for an internalcombustion engine according to claim 11, wherein a gear element of thereduction gear mechanism attached at the side of the throttle shaft is afan shaped gear.
 13. A throttle device for an internal combustion enginecomprising:a motor used as an actuator which drives a throttle shaft fora throttle valve; a first stopper for setting a fully closed position ofthe throttle valve; a first lever fitted at an end of the throttle shaftso as to permit a rotational movement with respect to the throttleshaft; a return spring which urges the first lever in a direction ofclosing of the throttle valve; a second lever which is secured to theend of the throttle shaft and is permitted to be engageable with thefirst lever by a spring force due to the return spring; a second stopperwhich sets a position where an initial opening degree of the throttlevalve, when no current is supplied to the motor, is larger than theopening degree of the fully closed position of the throttle valve andprevents the first lever from rotating in the direction of closing fromthe position of the initial opening degree; a spring used fordetermining the initial opening degree which provides a throttle valveopening force to the throttle shaft so as to keep the initial openingdegree; an acceleration shaft which is disposed in an off-set positionwith respect to the throttle shaft and is interlockable with anacceleration pedal; and a third lever serving as an acceleration leverused for a limp-home function arranged to rotate integrally with theacceleration shaft and is engageable with the first lever when theacceleration pedal rotates beyond a predetermined rotation angle so asto activate a self-pulling function with the acceleration pedal when themotor is inoperable due to malfunctioning of an electric throttlecontrol system.
 14. A throttle device for an internal combustion engineaccording to claim 13, wherein, with a throttle valve opening degreecharacteristic for the limp-home function defined by a relationshipbetween throttle valve opening degree and acceleration shaft rotationalangle, the third lever is formed by a cam lever which modifies and setsthe throttle valve opening degree characteristic at the intermediateportion thereof as a non-linear characteristic which is below a linearcharacteristic having a predetermined inclination.
 15. A throttle devicefor an internal combustion engine which includes a motor used as anactuator in a throttle control system, a fully closed position settingmechanism for setting a fully closed position of a throttle valve, andan initial opening degree setting mechanism which keeps an initialopening degree of the throttle valve larger than that of the fullyclosed position when no current is supplied to the motor, wherein areduction gear mechanism of the motor which drives a throttle shaft forthe throttle valve is disposed at one of the side walls of a throttlebody for the throttle valve, a casing portion is formed at the oppositeside wall of the one side wall of the throttle body, an end of thethrottle shaft and an acceleration shaft interlocked with anacceleration pedal are introduced into the casing portion, a throttleposition sensor, acceleration pedal position sensor and the initialopening degree setting mechanism are installed within the casingportion, and a member supporting the acceleration shaft and accelerationpedal position sensor constitutes as a cover of the casing portion. 16.A throttle device for an internal combustion engine according to claim15, wherein a movable element of the throttle position sensor isinmovably arranged at the throttle shaft, a stationary element thereofis inmovably arranged at a side wall of the throttle body, a movableelement of the acceleration pedal position sensor is inmovably arrangedat the acceleration shaft, and a stationary member thereof is formed onan inner wall of the cover.
 17. A throttle device for an internalcombustion engine according to claim 15, wherein the throttle shaft isarranged in an off-set position with respect to the acceleration shaft,and a limp-home mechanism, configured to cause the throttle shaft toengage with the acceleration shaft when the motor is inoperative and theacceleration shaft rotates beyond a predetermined rotational angle so asto permit transmission of a driving force through the accelerationshaft, is arranged inside the casing portion.
 18. A throttle device foran internal combustion engine according to claim 16, wherein thethrottle shaft is arranged in an off-set position with respect to theacceleration shaft, and a limp-home mechanism, configured to cause thethrottle shaft to engage with the acceleration shaft when the motor isinoperative and the acceleration shaft rotates beyond a predeterminedrotational angle so as to permit transmission of a driving force throughthe acceleration shaft, is arranged inside the casing portion.
 19. Athrottle device for an internal combustion engine according to claim 11,wherein the engine includes a motor used as an actuator for driving athrottle valve and a reduction mechanism, a throttle position sensor fordetecting a position relating to the opening degree of the throttlevalve, and an initial opening degree setting mechanism which keeps aninitial opening degree of the throttle valve larger than that of thefully closed position when current is not supplied to the motor, whereinthe reduction gear mechanism and the initial opening degree settingmechanism are disposed at one side with reference to a throttle body forthe throttle valve, and the throttle position sensor is disposed atanother side with reference to the throttle body.
 20. A throttle devicefor an internal combustion engine which includes a motor used as anactuator for driving a throttle valve, a fully closed position settingmechanism for setting a fully closed position of the throttle valve, astopper used for setting an initial opening degree which keeps aninitial opening degree of the throttle valve larger than that of thefully closed position when no current is supplied to the motor, a firsturging device which urges the throttle valve in a closing directionthereof in a region beyond a throttle valve opening degree defined bythe stopper used for setting a throttle initial opening degree, and asecond urging device which urges the throttle valve in its openingdirection so as to keep the throttle initial opening degree near thefully closed position thereof, wherein when assuming that a shaft torquein the direction of the closing the throttle valve provided by the firsturging means at the position of the stopper used for setting the initialopening degree is T1 and another shaft torque in the direction ofopening the throttle valve provided by the second urging means at theposition of the stopper used for setting the initial opening degree isT2, the following inequations are satisfied;

    T1≧Mf×Ge+Vf

    T2≦Mf×Ge+Vf

wherein, Mf; friction torque when the motor is standstill, Ge; reductiongear ratio, Vf; necessary torque to be applied on the throttle shaft soas to open the throttle valve.